### Please describe the problem.
Adb special remote does not preserve remote timestamp on "import".
Therefore files downloaded several days ago lose their real mtime when transferred to PC,
and from that moment onward files on android will have mtime different from stored in annex/symlinks.

But all files already present in PC repo -- during "export" correctly propagate their mtime to android.

### What steps will reproduce the problem?

[[!format sh """
git annex initremote android type=adb androiddirectory=/storage/0000-0000/books encryption=none exporttree=yes importtree=yes
git config remote.android.annex-sync false
git config remote.android.annex-tracking-branch main
git annex export main --to android
# ADD: download some "file" through android into "books"
git annex sync --content android
stat -c%y "file"
Modify: 2022-01-01 20:51:11.487603199 +0200
"""]]

### What version of git-annex are you using? On what operating system?
git-annex version: 8.20211118-g23ee48898
ArchLinux 5.15.12-arch1-1

### Please provide any additional information below.
Most likely can be fixed by:

[[!format diff """
--- i/Remote/Adb.hs
+++ w/Remote/Adb.hs
@@ -202,6 +202,7 @@ retrieve' serial src dest =
                showOutput -- make way for adb pull output
                liftIO $ boolSystem "adb" $ mkAdbCommand serial
                        [ Param "pull"
+                      , Param "-a"
                        , File $ fromAndroidPath src
                        , File dest
                        ]
"""]]

### Have you had any luck using git-annex before?

Nice work fixing earlier notorious bug, it made the ADB special remote usable for me at least in PC -> android direction! :)  
[[https://git-annex.branchable.com/forum/Mixed_content_repos_with_import_and_export/#comment-764ac971faf756140055333649ffb94c]]
